1. Field of the Invention
The invention concerns novel amido peroxycarboxylic acids and their use as bleaches, especially in the cleaning of fabrics.
2. The Related Art
Organic peroxyacids have long been known for their excellent bleaching activity. For instance, U.S. Pat. No. 4,642,198 (Humphreys et al) describes a variety of water-insoluble organic peroxyacids intended for suspension in an aqueous, low pH liquid. The preferred peroxy material is 1,12-diperoxydodecanedioic acid (DPDA). Surfactants, both anionic and nonionic, were utilized as suspending agents for the peroxyacid particles. When formulated with 10% surfactant, the peracid had good stability under storage conditions. When the surfactant level of the formulation was increased to 22%, a level typical for a heavy-duty laundry detergent, the half-life of the DPDA decreased dramatically. For example, U.S. Pat. No. 4,992,194 (Liberti et al) reports that at 40.degree. C. the half-life of DPDA was only 1 to 2 weeks in a pH 4-4.5 heavy-duty laundry liquid.
Another effective peracid is 4,4'-sulfonylbisperoxybenzoic acid (SBPB) reported in EP 0 267 175 (Dyroff et al) as possessing superior storage stability. U.S. Pat. No. 4,822,510 (Madison et al) demonstrates the increased stability of SBPB over DPDA in an aqueous liquid bleaching composition.
U.S. Pat. No. 4,634,551 (Burns et al) and U.S. Pat. No. 4,686,063 (Burns) describe peroxyacids having polar amide links along a hydrophobic backbone. These substances are stabilized with an exotherm control agent selected from boric acid and urea. Described in detail are a variety of n-acyl aminoperoxy acids and alkylamino oxoperoxy acids. All of the reported substances are mono-percarboxylic acids. A related patent, EP 0 349 220 (P&G), suggests use of a phosphate buffer solution and a pH between about 3.5 and 6 for improving storage stability of amido peroxyacids.
EP 0 349 940 (Hoechst AG) describes a series of imido peroxyacids, chief among which is N-phthaloylamino peroxycaproic acid (PAP). Suspension of imidoperoxycarboxylic acids in an aqueous system is achieved through use of sodium alkylbenzene sulfonate as reported in EP 0 435 379 (Akzo N.V.). Related technology in EP 0 347 724 (Ausimont) discloses heterocyclic peracids such as N-acyl-piperidine percarboxylic acids. WO 90/14336 (Interox) discloses 6,6'-terephthaldi(amidoperoxyhexanoic) acid and 6,6'-fumaryl bis(amidoperoxyhexanoic) acids.
Although many of the amido and imido peroxyacids have a quite dramatic bleaching activity, their stability in surfactant solutions remains a considerable problem. Clearly there is a need for new peracids specifically designed for heavy-duty laundry liquids. The materials also need to be physically stable in terms of thermal and shock sensitivity and in terms of storage stability.
In view of the problems of the art, it is an object of the present invention to provide new peroxycarboxylic acids with effective bleach activity.
Another object of the present invention is to provide peroxycarboxylic acids with superior storage stability.
Still another object of the present invention is to provide new peroxycarboxylic acids that, in addition to excellent activity, are also characterized by good storage stability when suspended in an aqueous medium.
A further object of the present invention is to provide a method of bleaching fabrics in a fully-formulated, heavy-duty laundry detergent composition through the use of new peroxycarboxylic acids.
These and other objects of the present invention will become more readily apparent through consideration of the following summary, detailed description and examples.